The invention relates generally to a weld joint and, more particularly to an apparatus and method for repairing or replacing a core spray line weld joint in a boiling water nuclear reactor.
A core spray piping system in operating boiling water reactors is typically of welded construction. The welds in the core spray system piping, however, are susceptible to intergranular stress corrosion cracking (IGSCC). As a consequence, welded pipe joints in the core spray line can become cracked.
Common to most operating reactors, the core spray cooling water is delivered to the reactor core region by piping internal to the reactor vessel. A portion of this internal piping is a horizontal segment that follows the radius of curvature of the reactor vessel wall. The proximal end of the horizontal piping is connected to a T-box at the core spray nozzle penetration. This weld is designated as the P3 weld. The distal end of the horizontal core spray line is welded to a short radius elbow. This weld joining the distal end of the core spray line to the short radius elbow is designated as the P4a weld. In at least one boiling water reactor design, there is another weld in the core spray line in close proximity to the T-box. This weld is designated as the P3a weld. An exemplary piping configuration near the vessel T-box is shown in FIG. 1.
In the event that cracking should occur in the P3a weld, the structural integrity of the core spray line, which delivers cooling water to the reactor core, would be lost. A preemptive repair would be desirable to prevent separation of the P3a weld in the event that circumferential through-wall cracking should occur at this weld location in the core spray line.